Daniel: (this is what I did as a kid to my dad and it did help him to stop)

He got an idea! One day you just kept finding your packs having a tape to keep it closed. Just would tear it open and have a smoke. But each time you took your pack would be more and more taped up, eventually every inch completely covered in tape so you couldn't even open it anymore without something sharp to cut it open. With time you got so fed up and knew it was a bad habit so began cutting down then stopped. Daniel felt very victorious for a looong time and still brags about it.

Zack:

You looked so cool to him! He always cringed when he walked past smokers but it does look cool. At first he always thought you looked cool and wanted to do it as well but then he matured and saw the bad effects it has on you so now he is trying to make you stop, finds it disgusting, and hopes you stop soon.

Jay:

Jay also smoked until someone told him he woudln't get a lover like that. But seeing you do it made him pick the habit back up as it's difficult not to do it when he sees you do it each time and tastes it when sharing a kiss. So if someone can't find either of you they can expect to find you both having a smoke outside.

Vasco:

He doesn't like it. Takes it out of your mouth each time and crushes it, at first it was occupied with a "don't smoke, it's bad for you" but now it's just narrowed eyes that say it instead of having to verbally do so. He doesn't like it, disapproves of it, so hopes him just doing this will eventually get you so annoyed you stop.

Jace: (Jace has a cameo in The Real Anti-Smoking Campaign where he tries to stop smoking)

Jace used to smoke but he went to a place to help him stop. So when he saw you doing it it gave him some trouble to resist the urge. Which is also why he might always react so harsh when you go to smoke as he doesn't want you to ruin your health and he hates that he has the urge to join you. He knows he can't stop you, that's something you have to decide. All he can do is just remind you of its dangers and recommend the place he went to to help him quit.

Johan:

He just watches, wondering why you do it, then asks what it tastes like. But when you offer it he declines. He seen the ads and stories of how terrible it is, he already has issues with his body, he doesn't need more. He doesn't like the smell though so can't be near him when having a smoke. He will be so blunt to say "stinks" when you light it so have to then walk away or stand where the wind doesn't go his way.

Jake:

He used to smoke a lot before Gun knocked out his teeth, then it became less and less. Now he'll only smoke few times when you are having one and offer. Sometimes he declines with a simple raised hand, other times he takes one. He's not stopping, just cutting down. He doesn't really care much if you smoke, almost everyone around him does so honestly not smoking would be more weird to him.

Gun:

He doesn't care. He smokes so he has no thoughts about you doing it. He knows it's bad but he doesn't care, only life once so do as you want. You are allowed to take from his pack. Sometimes to light his cigarette he takes your chin and puts his cigarette end to yours.

Goo:

Goo avoids you as he hates cigarettes and has you first brush your teeth or eat a mint before kissing him. When you smoke aside him he cringes, walks away, and/or slaps it out of your mouth and just says a "stop" or "no".